Speed up opening folios with photos: decode their pictures in parallel

Each picture of a folio was decoded in turn while its item was built, a quarter of a second for a 12 megapixel photo. Diagram::fromXml() now reads every picture of the folio first, decodes them all at once on a pool of its own (one thread per core, at most one per picture), then builds the items in file order in the GUI thread as before. The decoding (base64 text, then the picture file) moves out of DiagramImageItem::fromXml() into decodePicture(), which touches only its argument. QImage::fromData() then QPixmap::fromImage() is what QPixmap::loadFromData() does, so the pixels are the same. On a 263 MB project with 22 photos on one folio: --info 21.3 s -> 12.5 s, the folio's content 10.6 s -> 3.2 s, opening its .qetz 15.6 s -> 9.3 s. Peak memory +220 MB (1.81 -> 2.03 GB), the pictures' text being converted by several threads at once. A resave is byte-identical to master's, and so is a PNG export. tst_folioimageload: six pictures come back with their own pixels and positions, and an <image> without a picture does not stop the others. It fails when the decoded pictures are handed to the wrong items. Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
2026-10-14 17:44:13 +02:00 · 2026-10-14 12:09:09 +13:00
parent 8b680af938
commit 6751fc6f19
5 changed files with 240 additions and 24 deletions
@@ -0,0 +1,132 @@
+/*
+	Copyright 2006-2026 The QElectroTech Team
+	This file is part of QElectroTech.
+
+	QElectroTech is free software: you can redistribute it and/or modify
+	it under the terms of the GNU General Public License as published by
+	the Free Software Foundation, either version 2 of the License, or
+	(at your option) any later version.
+
+	QElectroTech is distributed in the hope that it will be useful,
+	but WITHOUT ANY WARRANTY; without even the implied warranty of
+	MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+	GNU General Public License for more details.
+
+	You should have received a copy of the GNU General Public License
+	along with QElectroTech.  If not, see <http://www.gnu.org/licenses/>.
+*/
+#include "qetapptest.h"
+#include "diagramcontent.h"
+#include "qetgraphicsitem/diagramimageitem.h"
+
+#include <QDomDocument>
+#include <QRandomGenerator>
+
+/**
+	Diagram::fromXml() decodes a folio's pictures in parallel, then builds
+	the items in file order. Every picture must come back with its own
+	pixels and position, whatever thread decoded it.
+*/
+class tst_folioimageload : public QObject
+{
+	Q_OBJECT
+
+	Diagram *m_diagram = nullptr;
+
+	/// A picture no other one equals: its own size and noise.
+	static QImage distinctImage(int n)
+	{
+		QImage image(40 + 7 * n, 30 + 3 * n, QImage::Format_ARGB32);
+		QRandomGenerator random(quint32(n + 1));
+		for (int y = 0 ; y < image.height() ; ++y)
+			for (int x = 0 ; x < image.width() ; ++x)
+				image.setPixel(x, y, random.generate() | 0xFF000000);
+		return image;
+	}
+
+	static QImage pixelsOf(const DiagramImageItem *item)
+	{
+		return item->pixmap().toImage()
+				.convertToFormat(QImage::Format_ARGB32);
+	}
+
+	void removePictures()
+	{
+			// A selected picture's handles are its children, in items()
+			// too: deleting the picture first would leave them dangling.
+		m_diagram->clearSelection();
+		for (QGraphicsItem *item : m_diagram->items())
+			if (item->type() == DiagramImageItem::Type)
+				delete item;
+	}
+
+private slots:
+	void initTestCase()
+	{
+		QVERIFY(QetAppTest::editor());
+		m_diagram = QetAppTest::diagram();
+		QVERIFY(m_diagram);
+	}
+
+	void cleanup()
+	{
+		m_diagram->clearSelection();
+		removePictures();
+		m_diagram->undoStack().clear();
+	}
+
+	void everyPictureComesBackWithItsPixels()
+	{
+		QHash<int, QImage> expected;	// by x position, each its own
+		for (int n = 0 ; n < 6 ; ++n) {
+			const QImage image = distinctImage(n);
+			auto *picture = new DiagramImageItem(QPixmap::fromImage(image));
+			m_diagram->addItem(picture);
+			picture->setPos(100 + 150 * n, 200);
+			picture->setSelected(true);
+			expected.insert(qRound(picture->pos().x()), image);
+		}
+		QDomDocument document = m_diagram->toXml(false);
+		removePictures();
+
+		DiagramContent content;
+		QVERIFY(m_diagram->fromXml(document, QPointF(), false, &content));
+
+		QCOMPARE(content.m_images.size(), expected.size());
+		for (const DiagramImageItem *picture : std::as_const(content.m_images)) {
+			const int x = qRound(picture->pos().x());
+			QVERIFY2(expected.contains(x), "picture moved");
+			QCOMPARE(picture->pos().y(), 200.0);
+			QCOMPARE(pixelsOf(picture), expected.value(x));
+		}
+	}
+
+	void anImageWithoutPictureDoesNotStopTheOthers()
+	{
+		for (int n = 0 ; n < 3 ; ++n) {
+			auto *picture = new DiagramImageItem(
+						QPixmap::fromImage(distinctImage(n)));
+			m_diagram->addItem(picture);
+			picture->setSelected(true);
+		}
+		QDomDocument document = m_diagram->toXml(false);
+		removePictures();
+		QDomElement images = document.documentElement()
+				.firstChildElement(QStringLiteral("images"));
+		QVERIFY(!images.isNull());
+		QDomElement empty = document.createElement(QStringLiteral("image"));
+		images.insertBefore(empty, images.firstChild());
+
+		DiagramContent content;
+		QVERIFY(m_diagram->fromXml(document, QPointF(), false, &content));
+
+		int with_pixels = 0;
+		for (const DiagramImageItem *picture : std::as_const(content.m_images))
+			if (!picture->pixmap().isNull())
+				++with_pixels;
+		QCOMPARE(with_pixels, 3);
+	}
+};
+
+QET_APP_TEST_MAIN(tst_folioimageload)
+#include "tst_folioimageload.moc"